DE102006008266A1 - Soil characteristic e.g. soil consistency, determining method, involves determining soil characteristic as dynamic deformation module by product of contact surface parameter and dynamic rigidity during compression process - Google Patents

Abstract

The method involves enabling contact of a contact unit (1) with soil (11) during a contact phase, and exposing contact force exerted by the soil. The dynamic rigidity of the soil is established from the gradients of the contact force and a contact path. A contact surface parameter is determined for consideration of an actual contact surface (12) with the soil. The soil characteristic is determined as a dynamic deformation module by the product of the parameter and the rigidity during a compression process with a soil compaction device. An independent claim is also included for a soil compaction device.

Description

The The invention relates to a method for determining a soil property by means of a soil compaction device, which has a swinging action Contact element for soil compaction has.

When Soil compacting devices are in particular vibrating plates and tampers, but also known as vibratory rollers. They each point at least one ground contact element, that of a vibration exciter is vibrated and initiates the vibration in the ground, thereby to achieve a compaction effect.

Around the goodness to be able to check a compaction work is It is helpful to have certain soil properties, such as the Soil stiffness, ductility, load bearing capacity or similar to investigate.

For determining soil parameters, methods and devices are known that operate separately from soil compaction equipment. Thus, there is a standardized plate printing method (DIN 18134), in which a deformation module E _{V is} determined as part of a static load plate pressure test. Likewise, a dynamic load plate pressure test is known (Technical Test Instructions for Soil and Rock in Road Construction TP BF-StB, Part B 8.3 (1997)).

conventional from the compaction equipment separate measuring methods and devices require a considerable Additional expenses, as in each case in addition to the compactor Measuring device made available Need to become, which usually require a properly trained operator. Besides that is the number of measurements on a defined area limits the time required, d. H. it can only be random be measured.

On the other hand, methods are also known in which special soil compaction devices themselves are used, in particular to measure soil rigidity and / or deformation moduli of the soil, which represent the central criterion for a compaction success. Such devices and methods are for example in the DE 27 10 811 C2 , WO 98/17865, DE 29 42 334 C2 such as EP 1 164 223 A1 known. These publications each show vibratory rollers, which are moved over the soil to be compacted and draw conclusions on the soil stiffness due to the vibration characteristics of the roller drum (drum bandage).

vibratory rollers are usually operated so that the ground contact element serving roller drums not even with oscillatory application lift off the ground. The roller bandages move in total periodically, resulting in a relatively uniform amplitude movement of the Roller bandage yields. For other soil compacting devices, in particular for vibratory plates or -stampers are the known measuring methods and devices not. Vibration plates and rammers usually lose while a significant portion of a vibration stress cycle the contact to the ground. This contact times have been found, the only make up about 10% of the total oscillation period. The above described, on vibratory rollers used measuring methods are on it aligned that the measured signals from a largely steady state arise. Even if the roller bandages should jump, the flight phases are relatively short, so the error influence is low.

at Rammers and vibratory plates, on the other hand, are of long flight phases and short contact times go out, so that designed for a periodic movement behavior Measuring methods of the prior art are unsuitable. Also subject the ground contact elements of vibratory plates and pestles one rather chaotic movement behavior, because they are jumping through or fly again and again ground forces in different places need to record.

Of the Invention is based on the object, a method for determining indicate soil properties that also apply to soil compaction devices is suitable whose ground contact element repeatedly lifts off the ground and especially even a longer one Flight phase - related on a vibration cycle - completed. The procedure should always include a determination of the soil parameters then allow, if independent from the concrete movement behavior and / or contact behavior of the soil compacting device while of an exciter cycle has contact with the ground. Preferred applications are soil compaction devices with rather chaotic movement behavior, in particular vibratory plates and rammers.

According to the invention Task solved by a method according to claim 1. A soil compaction device utilizing the method defined in claim 29. Advantageous developments of the invention are in the dependent claims specified.

An inventive method is used to determine a soil property by means of a soil compacting device, which has a swinging acted upon contact element for soil compaction. The contact element touches the ground during a contact phase and is exposed to a contact force F _contact exerted by the ground and resets a contact path s _contact . In the following, the contact force F _contact is also referred to simply as the contact force F and the contact path s _contact as the contact path s.

The Soil compacting device may be a vibrating plate or a Be vibration rammer. It has a comprehensive contact element Lower mass and one usually a drive comprehensive upper mass. The lower mass is over one Spring device coupled to the upper mass. Component of the lower mass can also, for. B. in a vibrating plate, a vibration exciter be, which acts on the contact element. In a vibratory rammer the vibration exciter by means of a path excitation, z. B. by a crank mechanism, between the upper mass and the lower mass is arranged.

ermittelt.The soil property, which can be determined by the method according to the invention, is referred to as the dynamic deformation modulus E _{V, dyn, compressor} and by the relationship

determined.

In this case, ΔF _contact / Δs _{contact represents} an approximation (averaging) to the actual gradient of the contact force dF _contact / ds _contact . Α is a contact surface parameter for taking into account the geometry and shape of the actual contact surface of the contact element with the ground during a particular, for the determination the actual contact area considered time period.

On the basis of the dynamic deformation modulus E _{V, dyn, compressor} , a dynamic shear modulus G _{V, dyn, compressor} can optionally be calculated taking into account soil-dependent parameters (transverse contraction number ν).

Of the Contact surface parameter α, which as Geometry factor reflects the influence of the actual contact surface, gets even closer below explained. Since the during a load cycle acting contact surface as well as the contact force and the relevant path of contact both in direction as well as their size of cycle to change cycle can, Both the contact surface parameters α and the contact force and the contact path during each load phase, so while every load cycle, determined.

The factor k _dyn represents the dynamic rigidity of the soil and is formed as a gradient of the contact force F and the contact path s. Also, the dynamic stiffness k _dyn , which can also change within the loading phase, is determined during each loading phase in order to be able to precisely monitor the rigidity of the soil during the compaction process.

To determine the dynamic stiffness k _dyn , the contact force and the contact path traveled by the contact element during the contact phase must first be determined.

Preferably become the components of the contact force F in the three spatial directions from the center of gravity sentence a fixed in the center of gravity of the contact element coordinate system certainly. Alternatively you can the components also for a fixed coordinate system, e.g. B. are determined with respect to the ground.

In the case of a moving coordinate system, the resulting acceleration components result from the sum of the external forces acting in the Z direction m U (ẍ S - ẏ S · Ṅ + ż S · Φ.) = ΣF X m U (ÿ S - ż S · Ẋ + ẋ S · Ṅ) = ΣF Y m U (z .. S - ẋ S · Φ. + ẏ S · Ẋ) = ΣF Z (2) where Φ, Ẋ and Ṅ represent the respective rotational speeds in the pitching direction (about the y-axis), rolling direction (about the x-axis) and yawing direction (about the z-axis) and m _U the mass of the contact element. ẋ _S , ẏ _S , ż _S represent the respective translation speeds in the center of gravity of the contact element, while ẍ S , ÿ S , z .. S represent the corresponding accelerations.

The forces acting on the lower mass are composed (with i = x, y, z) from the respective force components due to an unbalance excitation F _{ECC, i} from the resulting contact force to the ground F _{c, i} from the cutting forces to the rest of the machine (e.g. Upper mass of the soil compacting device) F _{U, i} as well as from the components of the weight of the contact element. The sum of the attacking forces can therefore be specified for the individual spatial directions as follows ΣF X = F C, X + F ECC, X + F U, X - m U · G · sin (Φ) · cos (X) ΣF Y = F C, Y + F ECC, Y + F U, Y + m U · G · cos (Φ) · sin (X) ΣF Z = F C, Z + F ECC, Z + F U, Z - m U · G · cos (Φ) · cos (X) (3) where F _{C, i is} a contact force of the contact element ( 1 ) to the bottom, F _{U, i} a cutting force between the contact element ( 1 ) and the rest of the machine (upper mass), m _{U is} the mass of the contact element, F _{ECC, i is} the exciting force of a vibrator exciting the contact element, and Φ and X represent the corresponding pitch or roll angle.

Substituting the two equation systems (2) and (3) above and dissolving according to the respective contact force component results F C, X = m U (ẍ S - ẏ S · Ṅ + ż S · Φ.) - F ECC, X - F U, X + m U · G · sin (Φ) · cos (X) F C, Y = m U (ÿ S - ż S · Ẋ + ẋ S · Ṅ) - F ECC, Y - F U, Y + m U · G · cos (Φ) · sin (X) F C, Z = m U (z .. S - ẋ S · Φ. + ẏ S · Ẋ) - F ECC, X - F U, Z + m U · G · cs (Φ) · cos (X) (4)

The total resulting contact force can then be calculated from the individual components F _{C, i} by determining the amplitude and direction of the total contact force corresponding vectorially from the subcomponents.

The inventive method let yourself z. B. in a vibrating plate or a Vibrationsstampfer use. As with such devices the contact force predominantly normal to the contact surface acts, is preferably the contact force component in the contact normal direction, ie in the direction of the z-axis by evaluating the momentum balance in determined this direction.

The contact force can then z. B. be determined to simplify F C, Z = m U · Z .. S - F ECC, Z (5) where m _{U is} the mass of the contact element, z .. S the acceleration of the contact element in the direction of the contact normal (z-axis) and F _{ECC, Z is} the exciting force of a vibration element acting on the contact element.

For determining the translatory accelerations and the spin accelerations:
The translational acceleration ẍ S , ÿ S , z .. S the contact element in the center of gravity can z. B. be measured by a provided on the contact element itself accelerometer. As accelerometer is z. B. a center-mounted triax transducers for measuring all three spatial directions simultaneously. The translational velocity components ẋ _S , ẏ _S , ż _S in the three spatial directions can then z. B. be determined by simple integration of the acceleration signals.

Alternatively - if z. B. due to the design no transducer can be mounted in the center of gravity - can be the translational acceleration of the center of gravity in the three spatial directions (x, y, z) and the rotational acceleration about the three axes x, y, z determined by at least six accelerometers. These are preferably distributed around the center of gravity of the contact element in such a way that in each case three acceleration pickups are arranged in the direction of a normal (z-direction) to the contact surface with respect to their measuring direction, but if possible are not arranged on a line. Three more acceleration Receivers are arranged so that they are also not mounted on a line, but with respect to their measuring direction in the direction of a tangential to the contact surface.

Out the kinematic relationship between acceleration in the center of gravity and the acceleration measured at any point on the body in the case of existing, i. measured spins Φ .., Ẍ and N .. let now both the desired translational accelerations as well as detect the spins. Leave the required angles of rotation Φ and X then determine by double integration of the spins Φ .., Ẍ.

In certain applications it may be sufficient, the number of sensors required to reduce because certain degrees of freedom account for design reasons. So leads the contact element of a vibration rammer, so the Bo denkontaktplatte, for example, due to the parallel leadership of the padfoot one Movement mainly in a translatory direction, namely in the direction of the contact normal (Z-axis). For this application is therefore u. U. the use of a single Acceleration sensor on the contact element sufficient. Further Movement components can optionally determined by sensors on the upper mass.

Also Alternatively, the acceleration components in the direction the contact normal also non-contact, For example, determine by optical laser sensors. The sensors are then preferably not on the contact element, but at one over a Federeinrichtung provided with the contact element upper mass. The upper mass can, for example, in a known manner a drive motor the soil compacting device. With the help of the sensors let yourself for example, a change in distance measure between the upper mass and the contact element, so at Knowledge of position and orientation of the upper mass over a two-fold derivative the accelerations of the contact element in Contact normal direction determined at the corresponding measuring points can be.

Finally, can also over Radar sensors the speed of the contact element relative to the upper mass z. B. due to the Doppler effect or the distance z. B. are determined by means of interference radar, which is also a Calculation of the accelerations, as described above, allows.

To determine the stimulating force F _ECC :
In one embodiment of the invention, the exciting force F _ECC coming from the vibration exciter may be measured by a force measuring device provided between the vibration exciter and the contact element. As a force measuring device is for example a load cell, which is mounted under the vibration exciter.

Alternatively, the exciting force F _{ECC can} also be calculated from the instantaneous position of the exciter unbalances. In the event that the vibration generator has two counter-rotating shafts with equal imbalance masses whose axes of rotation have the same orientation as the Y-axis of the contact element and whose phase position is adjustable to each other, calculate the components of the exciting force F _ECC Contact element fixed coordinate system as a function of time t simplified by the following relationship F ECC, X (t) = EM · Ω 2 sin (φ phase / 2) · cos (Ω · t) F ECC, Y (t) = 0 F ECC, Z (t) = EM · Ω 2 cos (φ phase / 2) · cos (Ω · t) (6) where EM is the resulting mass of a rotating imbalance mass, Ω is the exciting frequency of the vibrator and φ _{phase represents} the phase angle between the two imbalance masses.

It can therefore from the current position of the imbalances and the knowledge the exciter shaft angular velocity and the magnitude of the imbalance determines the currently acting unbalance force in direction and size become.

Of course, the stimulating force F _ECC can also be calculated with differently designed vibration exciters. It is usually represented as a function of time t, but can also be made dependent on the phase position or angular position of the imbalance masses involved.

In the case of the above-mentioned vibrating plate or a vibration rammer can be used to determine the exciting force F _ECC z. B. acting exclusively with the contact normal direction Component F _{ECC, Z are} calculated, since this only the excitation in the direction of the z-axis is important, so the normal to the contact surface.

The phase angle φ _phase , ie the relative phase position of the two imbalance masses to each other, is variable depending on the setting of the operator. The position of the imbalances can be determined, for example, by proximity sensors (inductive, Hall sensors). The angular velocities of the imbalance shafts can then be determined from the positions of the imbalances.

The cutting forces F _{U, i} between the contact element and the rest of the machine can be z. B. by means of load cells, between the contact element and z. B. the upper mass of the soil compacting device are arranged.

For determining the contact path s:
The contact path s required for the determination of the dynamic stiffness k _dyn is determined at the points in time at which the contact element transmits ground contact forces, preferably in the vicinity of the resulting force application point, since the path of the point of application of force is most closely related to the change of the acting contact force is connected. The determination of the position of the force application point will be described below.

to Determining the contact path will first be the accelerations of the Determined force application point. By double integration of the accelerations At the force application point can then be amplitude and direction of the Determine the path at the force application point (contact path).

berechnen.It is therefore necessary to first determine the position of the force application point P, which will be explained below in connection with the calculation of the contact surface parameter α. At the thus determined position of the force application point SP → = [SP X , SP Y , SP Z ] T (relative to a coordinate system in the center of gravity S), the acceleration can be in the force application point a → P from the kinematic relationships according to

to calculate.

sowie die Translationsbeschleunigung im Schwerpunkt a →S = [ẌS, ŸS, Z ..S]T lässt sich, wie bereits oben beschrieben, durch geeignete Sensorik, die z. B. auf dem Kontaktelement angeordnet sein kann, ermitteln. Vorzugsweise wird dabei jedoch nur der Kontaktweg in Richtung der resultierenden Kontaktkraft für die Auswertung berücksichtigt.The vector of the rotational speeds ω → = [Φ., Ẋ, Ṅ] T and the spins

as well as the translation acceleration in the center of gravity a → S = [Ẍ S , Ÿ S , Z .. S ] T can be, as already described above, by suitable sensors, the z. B. can be arranged on the contact element, determine. Preferably, however, only the contact path in the direction of the resulting contact force is taken into account for the evaluation.

If z. B. the contact force in a vibration plate predominantly normal to the contact surface acts, the contact path is preferably determined at the point of the force application point in the contact normal direction by evaluating the translational and the rotational motion components. The evaluation of equation (7) for the component of the acceleration in the point P (force application point) in the z-direction gives (neglecting the yawing motion, ie N .. = Ṅ = 0): a P, e.g. = z .. s + Ẍ · SP Y - φ .. · SP X - (φ. 2 + Ẋ 2 ) · SP Z (8th)

Double integration of a _{P, z} then provides the desired contact path s in the contact normal direction.

For the determination become the translational or rotational movement components, as already described above, for. B. three acceleration sensors so arranged on the contact element that they are not on a line lie, but with respect to their direction of measurement in the direction of a Normal to the contact surface attached are.

On this way you can for different Measuring times several pairs of measuring points from the contact force F and the associated Contact path s are formed.

This information is in a particularly advantageous manner for different times in each case the contact force F and the associated contact path s before, so that in each case a pair of measuring points from the contact force F and the contact path s can be formed for a time.

Preferably those measuring point pairs are determined during a Stress phase incurred in the contact element increasingly against pressed the ground becomes. In this connection can Measuring point pairs during a discharge phase in which the contact element is relieved, or a flight phase in which the contact element is in the air, without touching the ground, excluded from further evaluation.

For the measuring point pairs of the loading phase, a gradient dF _contact // ds _{contact is} formed which corresponds to the dynamic stiffness k _dyn valid at that time. The gradient dF / ds can also be formed as a ratio of two temporal changes (the force and the path).

Preferably, however, the resulting gradient for the respective pairs of measurement points are averaged by a statistical method, so that the resulting mean value can be determined as the relevant dynamic stiffness k _dyn .

Alternatively or additionally, depending on the time t for the contact force F and the contact path s, a phase diagram can be formed by calculation. For the part of the phase diagram that represents a loading phase in which the contact element is increasingly pressing against the ground, a mean gradient dF / ds is formed which represents the dynamic stiffness k _dyn .

To determine the contact surface parameter α:
As already stated above, to determine the dynamic deformation _modulus E _{V, dynVerdichter} , a contact surface _{parameter α is} also required to take account of the actual contact surface of the contact _element with the ground. Advantageously, the contact surface parameter α is determined on the basis of a calculated position of a force application point of the contact force F.

The Contact element, in particular a ground contact plate in a vibrating plate or a tamper, has a footprint that is at a standstill the soil compacting device is in contact with the ground. In operation, however, while the method of the invention is to come to the application is, as a rule, not the entire Floor space of the contact element during transmission be involved in the contact force, but only a partial area, namely the actual Contact area.

by virtue of the stamped by cyclic flight phases of the contact element locomotion and the associated skew of the ground contact element with respect to the surface of the soil to be compacted but also due to an inclination the surface itself is only a part of the bottom of the contact element in Contact with the ground while the remaining part sticks out in the air. In practice this can mean in a soil compacting device having a contact element, this is a rectangular base which completely touches the ground at standstill, in Operation, however, given only an actual contact surface which is less than one third of the floor area. The actual contact surface can although then also rectangular, triangular or by others Geometry, however, be considerably smaller than the base area. The contact surface does not have to be like in the standard plate printing process but can be concave in the different directions (axes) or convex. Furthermore, it can be within the current one actual contact area Enter areas where due to the current speed distribution there is little or no transmission of contact forces at the contact element. These must be considered in the determination of the relevant contact surface.

There the size of the momentary actual contact area has a decisive influence on the size of the transferable contact forces (at a larger contact surface can with otherwise identical, isotropic soil characteristics, transfer a larger contact force it must be for the determination of the deformation moduli are taken into account.

Since the actual contact surface of a considered time step in an exciter oscillation cycle with respect to the base of the contact element will not be arranged symmetrically, but z. B. in a - relative to the main direction of the soil compacting device - rear portion of the contact element, the resulting from the ground contact voltage contact force F does not act on the centroid of the base of the contact element, but at a remote location, namely in particular at or near a centroid of the actual contact area. Due to this deviation of Both centers of gravity or deviation of the force application point from the center of gravity of the contact element act on the contact element additional forces and moments that must be taken into account for detecting the soil properties.

The Size and geometry the contact area changes while of contact. If z. B. a rectangular contact element at the beginning a contact phase with a corner (triangular contact surface) the Ground touched, so it increases the triangular area first through the penetration. The inclination of the contact element will be subsequently so change that his focus of contact (contact surface and force) during the Intrusion moves. He will first become the focus of the contact element move back. Under certain conditions, the focus of contact may be but also over shift the focus of the contact element out. In extreme cases the contact element works within an exciter oscillation period to the opposite Corner.

The Contact element experiences through the eccentric force application point an additional Spin, the moment of inertia of the contact element counteracts.

wobei γ ein Wert in einem Bereich von 1,5 bis 2,7, insbesondere der Wert 2,1 ist und r_hyd den hydraulischen Vergleichsradius darstellt und sich gemäß

aus der tatsächlich wirksamen Kontaktfläche A_C berechnen lässt.It has been found that the contact surface parameter α can advantageously be determined according to the following relationship:

where γ is a value in a range from 1.5 to 2.7, in particular the value 2.1 and r _{hyd represents} the hydraulic comparison radius and according to

from the actual effective contact area A _C can be calculated.

there For determining the contact surface parameter α, a centroid can be used the actual contact area of the contact element with the ground to be determined from a Force application point of the contact force F is determined. The contact force F is a surface load, the on the contact surface the contact element acts. It can be caused by a resulting Force are imaged at the resulting force application point attacks. This force application point can be approximated as identical to the centroid the actual contact area be considered. To correct the deviation of the actual force application point from the center of gravity the contact surface may introduce a correction factor be, the z. B. is determined by simulation.

at an embodiment the invention, the movement of the contact element during the Ground contact detected by sensor. On the basis of the sensors determined information as well as due to the contact force F can the location and the dimension of within the footprint of the Contact element lying actual contact area and / or the force application point of the resulting contact force be determined.

The Sensors should be sensors that perform linear and / or rotational movements of the contact element with respect can capture different degrees of freedom.

It a sensor may be provided, with the one by the contact force F caused Nick spin of the contact element with respect to a standing transversely to the direction of travel of the soil compaction device Nick axis (y-axis) is determined.

Under circumstances must be caused by the contact force pitch or roll acceleration (about the x-axis) with knowledge of the exciting excitation torque the measured spins are calculated. Similarly can for detecting a rolling spin of the contact element with regard to one in the direction of travel extending roll axis (x-axis) also a suitable sensor can be provided. The pitch axis and The roll axis preferably extends through the center of gravity of the contact element. For measuring pitch and roll spins can but also three pickups that are not mounted on a line, but with regard to their measuring direction in the direction of the contact normal aligned (as described above).

In addition, can be it useful when measuring a translational movement of the contact element in Direction of the contact force F a corresponding sensor available is.

by virtue of the movements of the contact element measured by the sensors, in particular due to the spin around the pitch and Roll axis can each set up angular momentum balances around the pitch axis and the roll axis are made, from which caused by the contact force F contact torques around the pitch axis and the roll axis taking into account the stimulating Torques z. B. due to a pathogen and the cutting moments to the rest of the machine.

by virtue of the thus determined contact torque and the already known Contact force F can be the lever arms of the contact force F with respect to Nick axis and the roll axis and thus the position of the force application point determine the contact force F.

The Position of the force application point of the contact force can in first approximation as Location of the centroid the contact surface Thus, the location of the centroid is also considered is known.

by virtue of the location of the centroid the contact surface or also the force application point and a given relationship the contact surface parameter α can be defined become. The relationship between the contact surface parameter α and the Location of the centroid or the point of application of force can in advance by the manufacturer the soil compaction device are determined by experiments, a meaningful To get relationship. The specification of this relationship can be found in Form of a table or even a mathematical relationship deposited become.

On this way, the contact surface parameter α during a determined each compression cycle of the contact element and in dependence of the size respectively Position of the contact surface constantly adjusted become.

After both the contact surface parameter α and the dynamic stiffness k _dyn have been determined in this way, the dynamic deformation _modulus E _{V, dynVerdichter} can be determined according to the formula given above.

If necessary, a correlation between the thus determined dynamic stiffness modulus E _{V, dynVerdichter} and the deformation _modules determinable with the aid of conventional measuring methods can be established with the aid of calibration measurements. Thus, for example, depending on certain soil conditions, tables can be set up which permit a transferability of the dynamic stiffness modulus determined by the method according to the invention to other deformation moduli determined by means of standardized measuring methods.

Also according to the invention a soil compaction device specified with one of a Drive driven vibration exciter, one of the vibration exciter acted upon contact element, during a vibration cycle the ground in phases of constantly touching and briefly from the can lift to compacting soil, and with a measuring system for Determining a soil property comprising at least one sensor for detecting a movement behavior of the contact element. The soil compacting device according to the invention is characterized characterized in that the measuring system according to the above-mentioned inventive method is operated.

advantageously, the soil compacting device is a vibrating plate or a rammer. An application on rollers is in principle also possible.

These and other advantages and features of the invention will become apparent below by way of example with the aid of the accompanying figures explained. Show it:

1a ) In a schematic side view of a vibration plate with a contact element, a vibration exciter and an accelerometer;

1b ) the contact element of 1a ) with a schematic representation of the imbalance waves of the vibration exciter;

2 a perspective view of the contact element of 1 ;

3 a phase diagram with the contact force F _contact and the vibration path s over time;

4a ) and b) a contact element in operation, with a small contact surface;

5a ) and b) a contact element in operation, with a large contact surface;

6 a schematic representation of forces and moments on a contact element (simplified);

7 geometric relationships on a contact element with a two-shaft vibration exciter;

8th a contact element with a triangular contact surface;

9 the contact element of 8th in the plan view;

10 a contact element with a square contact surface;

11 the contact element of 10 in the plan view;

12 a plan view of a contact element with pentagonal contact surface; and

13 in a schematic side view serving as Bodenverdichtungsvorrichtung vibration tampers.

1 shows in highly simplified schematic representation serving as a soil compaction vibration plate with a contact element 1 , The contact element 1 may also be part of a vibration rammer in the same way. The contact element thus serving as a ground contact plate transmits, in a known manner, vibrational forces generated by a vibration exciter 2 be generated in the soil to be compacted.

As 1b ), the vibration exciter can 2 in a known manner from two counter rotating unbalanced shafts 3 exist whose phase position is mutually variable in order to achieve a steerability or a change in direction of the soil compaction device while driving.

The contact element 1 is about a spring device 4 with an upper mass 5 movably coupled. In the upper mass 5 is usually a drive for the vibration exciter 2 accommodated.

In 1a ) is also a sensor 6 shown, which can be formed for example by an accelerometer. The sensor 6 can be at the vibration exciter 2 or directly to the contact element 1 to be appropriate.

2 shows a part of the structure of 1a ) in perspective view.

The contact element 1 is greatly simplified as a rectangular plate reproduced. Instead of a single sensor 6 are six sensors 7 on the contact element 1 arranged, which can also be designed as an accelerometer.

In 2 is also a transverse to a direction X extending pitch axis 8th (Y-axis) and extending in the direction of travel X roll axis 9 (x-axis) drawn. The pitch axis 8th and the roll axis 9 intersect in a focal point 10 of the contact element 1 , The accelerometer 7 are each at a distance to the pitch axis 8th and the roll axis 9 arranged to rotate with respect to the pitch axis 8th and the roll axis 9 to be able to detect, in particular, rotational angles or rotational accelerations.

The invention now relates to a measuring method for determining a dynamic deformation modulus of the soil compacted by the soil compacting device. For this purpose, the movement behavior of the contact element 1 measured and evaluated in a suitable form, as described below. However, since the measuring method has already been explained in detail above in the introduction, only the essential aspects of the measurement method are merged below summarizes.

The dynamic deformation modulus is determined by the formula

K _dyn corresponds to the dynamic rigidity of the soil. The contact surface parameter α takes into account as geometric factor the characteristic size of the contact surface and in particular the deviation of the position of the force application point in relation to the total base area of the contact element. Both the dynamic stiffness k _dyn and the contact surface parameter α can be determined during each load phase, so that an always current evaluation of these parameters and thus of the dynamic deformation _module E _{V, dynVerdichter is} possible.

To determine the dynamic stiffness k _dyn , the contact force F _contact and that of the contact _element must first be determined 1 during the contact phase, ie during the contact of the soil to be compacted path s _{contact are} determined.

The contact force F _{contact is} determined from the set of center of gravity with respect to one on the contact element 1 fixed coordinate system. In addition to the center of gravity acceleration and the known mass of the contact element, the direction and magnitude of the exciting forces of the vibration exciter must 2 , Direction and size of the cutting forces to the rest of the machine, weight forces and the normal Beschleungiungskräften resulting from the rotational speeds are determined.

In particular, the contact force F _{contact is} simply calculated for the case of 1 shown vibration plate F contact = m L · Z .. L - F ECC (5) where m _{L is} the mass of the contact element 1 . z .. L the acceleration of the contact element 1 in the direction of the contact normal and F _ECC the stimulating force of the contact element 1 acting vibrator 2 is.

The translational acceleration z .. L of the contact element 1 in the contact surface normal direction can be, for example, via the sensor 6 (Acceleration sensor) in the center of gravity 10 of the contact element 1 measure (cf. 1a ).

Alternatively, the translational and rotational acceleration in the contact normal direction and in the direction of the pitch and roll axis can also be with the help of six sensors 7 (Accelerometers), which are used in the in 2 shown way z. B. to the center of gravity 10 of the contact element are attached determine.

Furthermore, the acceleration in the direction of the contact normal can also be determined without contact, that is to say for example by optical laser sensors or with the aid of the Doppler effect, with corresponding sensors 6a preferably at the upper mass 5 the soil compacting device are mounted.

The stimulating force F _ECC required for the calculation of the contact force F _contact in the above formula can be calculated by the following relationship: F ECC = EM · Ω 2 * Cos (φ phase / 2) · cos (Ω · t) where EM is the resulting mass of rotating unbalanced shafts 3 Ω is the exciting frequency of the vibration exciter 2 and φ _phase the phase angle between the two unbalanced shafts 3 represents.

The phase angle φ _phase is variable depending on the setting of the operator. It concerns the relative position of the two unbalanced shafts 3 to each other and can therefore be changed depending on the desired direction of travel (forward, backward) by the operator. A measurement of the phase angle φ _phase is possible, for example, by inductive or capacitive proximity switches or Hall sensors. It is also possible the adjustment of the phase position of the unbalanced shafts 3 with the help of a control valve, so that also secured information about the phase angle φ _phase are present.

If the contact force F _contact calculated according to equation (5) is _plotted over the oscillation path s for the course of time during a load cycle, this results in 3 illustrated, typical contact force / vibration displacement phase diagram. 3 distinguishes a movement cycle of the contact element 1 in two phases, namely an aerial phase (also called flight phase) and a contact phase, which has a loading phase and a discharge phase. During the aerial phase, the contact element flies 1 via the bottom to be compacted, while in the contact phase an interaction between the contact element 1 and the soil takes place.

As zero position, the point with the oscillation s = 0 is considered. Starting from this point is due to the imbalance of the vibration exciter 2 the contact element 1 pressed into the ground, so that according to the rising branch (see arrow direction in 3 ) with increasing vibration path an increase in the contact force F _contact sets. After reaching a maximum, the contact element 1 relieved due to the imbalance effect, so that the phase course reaches the descending branch of the contact phase, until finally no more ground contact exists (in 3 at s = 2).

Due to the vibration effect, the contact element 1 lifted from the soil to be compacted and moves - without contact with the ground and thus without contact force - flying over the ground.

After a change of the direction of vibration reaches the contact element 1 in the air phase, the zero position again, so that a new compression cycle begins.

The oscillation path s in the contact phase is referred to as the contact path s _contact . It can be calculated by double integration of the acceleration of the contact element. As stated above, the translational and rotational motion components should be taken into account, ie correspondingly also during the integration.

To determine the dynamic stiffness of the ground k _dyn , several measuring point pairs (contact force F, contact path s) in the loading _phase can now be determined and their gradient dF / ds determined. For this purpose, for example, the curve can be approximated by a polynomial with the aid of the least squares. The gradient of the approximated curve can then be calculated quite simply analytically from the polynomial coefficients.

The dynamic stiffness k _dyn is then determined by averaging the various gradients over the entire range of the loading phase, so that finally a k _dyn value can be found for a load cycle as a measure of the dynamic stiffness, which is a substantial part of the dynamic deformation modulus E _{V, dynVerdichter} according to equation (1) represents.

to Determination of the contact surface parameter α is initially on pointed out the following problems:

4a ) shows simplified the ground contact element 1 in operation during the compaction of a soil 11 , Due to the effect of the vibration exciter 2 is the contact element 1 opposite the soil surface 11 tilted so that only a rear part of the contact element 1 the ground 11 touched. Accordingly, in 4a ) a contact surface 12 plotted the actual contact of the contact element 1 with the ground 11 reproduces. In the contact area 12 contact forces act 13 as area load.

In 4b ) become the contact forces 13 as the resulting contact force 14 summarized in the contact surface normal direction at a force application point 15 acts and corresponds to the above contact force F _contact . The force application point 15 at which the contact force 14 on the contact element 1 attacks, has a distance a to the center of gravity 10 of the contact element.

For the focus 10 of the contact element 1 becomes the mass of the contact element 1 and the vibrator 2 considered.

It is well recognizable that the force application point 15 not with a centroid of a base of the contact element 1 coincides, which would result if the contact element 1 completely in contact with the ground. Rather, the contact force acts 14 unsymmetrical or eccentric to the centroid of the contact element 1 and also on the overall focus 10 of the contact element 1 ,

5 shows in analogy to 4 a contact element 1 that on a floor 11 acts, with the contact surface 12 is significantly larger (see 5a )). This is the case, for example, when the soil is softer than at 4a ).

How out 5a ), then the force application point shifts 15 the resulting contact force 14 closer to the center of gravity 10 so that the distance a is reduced.

For the determination of the contact surface parameter α can now, for example, the position of the force application point 15 the contact force 14 in relation to the location of the center of gravity 10 of the contact element 1 be used. Background of this approach is the consideration that with almost constant soil stiffness ent long the compression path of the centroid of a large contact area 12 ( 5a )) closer to the center of gravity 10 of the contact element 1 than with a small contact area ( 4a )).

To the center of gravity of the actual contact surface 12 To determine, first by the contact force 14 caused spin around the pitch and roll axis (reference numeral 8th and 9 in 2 ). From the knowledge of the currently resulting contact force 14 and the torques caused thereby may be the force application point 15 be calculated. For this purpose, the translational, the pitching and the rolling movement of the contact element 1 be determined by means of sensors. These are, for example, in 2 shown sensor 7 ,

The rotational movements occurring due to the contact, in particular so the pitch and roll movement of the contact element 1 , can be determined from the angular momentum balances in pitch and roll direction with knowledge of the a priori known moments of inertia of the contact element on the contact element 1 determine, so that by the contact force 14 caused contact torques about the pitch axis 8th and the roll axis 9 calculate, as explained later.

From the contact torques turn, with knowledge of the contact force 14 or F _contact according to the lever arms of the contact force 14 in the roll and pitch direction and thus the position of the force application point 15 be determined. It is from the knowledge of the center of gravity of the contact force to close the position and geometry of the contact surface. Since the ground can be uneven, this is not always possible in all cases. However, it is technically sufficient to establish a connection by suitable tests and statistical evaluation of the load cycles.

The conditions are simplified in 6 for the application of a vibrating plate shown.

In general, for the calculation of the contact surface parameter α, the position of the theoretical force application point must first be determined 13 be calculated:
Using the spin set, the rotational acceleration in the center of gravity of a moving body with respect to a coordinate system fixed in the center of gravity can be determined from the sum of the acting external torques I X · Ẍ + (I Z - I Y ) · Φ .Ṅ - (N .. + ẊΦ.) · I XZ + (Ṅ 2 - Φ. 2 ) · I Y Z + (ẊṄ - Φ ..) · I XY = ΣM X I Y · Φ .. + (I X - I Z ) · ṄẊ - (Ẍ + Φ .Ṅ) · I XY + (Ẋ 2 - Ṅ 2 ) · I ZX + (Φ.Ẋ - N ..) · I Y Z = ΣM Y I Z · N .. + (I Y - I X ) · ẊΦ. - (Φ .. + ẊṄ) · I Y Z + (Φ. 2 - Ẋ 2 ) · I XY + (ṄΦ.-Ẍ) · I ZX = ΣM Z (11) to calculate. The moments of inertia of the contact element I, I _X , I _Y , I _Z , etc. can be determined from CAD data or possibly also experimentally. The spins can be adjusted by suitably positioned acceleration sensors 7 , as described above, determine.

The components of the attacking torques result from the cutting moments M _U to the rest of the soil compaction device (upper mass), the moments M _C caused by the ground contact force and from the vibration exciter 2 applied moments M _ECC about the respective axes x, y and z according to .sigma..sub.m X = M C, X + M ECC, X + MU, X ΣM Y = M C, Y + M ECC, Y + M U, Y .sigma..sub.m Z = M C, Z + M ECC, Z + M U, Z (12)

For the ground contact by the force components F _{C, i} caused torques M _{C i} can start M C, X = F C, Z · r C, Y - F C, Y · r C, Z M C, Y = -F C, Z · r C, X - F C, X · r C, Z M C, Z = F C, Y · r C, X - FX C, X · r C, Y (13) where r _{C is} the coordinates of the force application point with respect to the center of gravity of the contact element 1 represent.

r _C are thus the coordinates that determine the position of the force application point 15 in relation to the center of gravity of the contact element 1 define. They can be determined by solving the above equation system (13), taking into account the equation systems (11) and (12).

This results in the coordinates r _{C of} the force application point 15 :
For the case of a contact element whose excitations lie in the xz plane of the center of gravity (ie F _{C, Y} ≈ 0), the following results for the lever arms:

r _{C, Z} is the z-coordinate of the underside of the contact element 1 and from z. B. CAD data known.

In the event that the vibration generator has two counter-rotating shafts with equal imbalance masses whose axes of rotation have the same orientation as the Y-axis of the contact element 1 and whose phase angle is adjustable relative to one another, the components of the exciting torque about the Y-axis (pitching moment) M _{ECC, Y} with respect to the coordinate system fixed on the contact element as a function of the time t are calculated by the following relationship M ECC, Y = EM · Ω 2 · [E z · (Sinφ V + sinφ H ) - r s · (Cos V + cosφ V )] (16)

EM is the resulting mass of the rotating imbalance mass 3 , Ω is the exciting frequency of the vibration exciter 2 , The angles φ _V and φ _H represent the instantaneous phase angles of the front and rear exciter shafts with respect to the vertical (z axis). B. separately by means of proximity switches on each exciter shaft. r _S represents half the distance of the exciter shaft centers and can be taken from CAD data or measured directly. e _Z represents the distance of the exciter center of gravity from the total center of gravity of the lower mass in the Z direction and can also be determined from CAD data.

The conditions are in 7 shown.

In the event that the center of gravity of the two excitation waves in the X and Y directions coincides with the center of gravity of the contact element, no additional exciting torques are produced by the exciter about the X axis and about the Z axis. The torque components M _{ECC, X} and M _{ECC, Z} are then zero. Of course, for any other case, the torques can also be computationally calculated from the instantaneous position of the imbalances.

The following is an example of a method for approximate determination of the actual contact surface 16 in the case of a rectangular and planar contact element 1 explains:
Due to the pitch and roll movement of the contact element, a contact will always emanate from a corner or edge of the contact element.

8th shows a schematic perspective view of a contact element 1 with direction of travel in the direction of the x-axis. On the contact element 1 is a triangular contact surface 16 drawn with dashed lines with straight boundary edges. Here are the outer boundary lines by the known outer geometry of the contact element 1 known.

The missing, in the idealized case straight inner boundary line (contact edge 17 ) is now made condition that the force application point 15 eg in the centroid of the contact surface 16 forming triangle is calculated.

9 shows the construction of the missing, inner edge of the contact surface 16 exemplary of a contact starting at a corner 18 (Intersection of the edges I and II of the contact element 1 ).

From the knowledge of the centroid (equal to the force application point 15 Therefore, the above determined coordinates r _C ) and the condition that the two lines g ₁ and g ₂ intersect at the centroid, can be at known coordinates of the two edges I and II of the contact element 1 set up a system of equations with two equations and the desired unknown intersection points (x _s1 , y _s1 ) and (x _s2 , y _s2 ) of the inner edge of the triangular contact surface 16 dissolve. The procedure is analogous if the contact is at another corner of the contact element 1 starts.

10 shows a case in which one of the so according to 9 calculated points of intersection on the actual geometry, ie in particular on the relevant edge of the contact element 1 wander out. Then the calculation of the inner contact edge 18 performed again, assuming that the contact surface 16 now quadrangular.

For the square contact surface 16 can now also from the known position of the centroid (coordinates r _{C of} the force application point 15 ) and the geometric design rules set up and solve a system of equations for the determination of the unknown intersections with the contact element edges (edges I and II).

11 shows the geometric determination of the centroid 15 a trapezoidal, quadrangular surface.

12 shows a case in which due to the superposition of the rotational and translational velocity components in one part 16a (dotted area) of the contact surface 16 , a velocity distribution arises at which this part moves away from the ground. Then these area proportions should have a lower valence in the calculation of the actual contact area 16 Be taken into account, since there are transmitted virtually no or very little ground contact forces.

Between the in 12 dotted area shown 16a moving away from the ground and in 12 hatched area part 16b , which moves to the ground, so transmits ground contact forces, runs a speed zero line 19 ,

The presence and location of the speed zero line 19 , in which the contact element speed reverses its sign in the normal direction, can be at a known translational and angular velocity of the center of gravity of the contact element 1 from the kinematic relationships. For the total velocity at a point (r _x , r _y ) of the contact element 1 with pure translation movement in the Z-direction and superimposed pitch / roll motion results ν P, e.g. = ż S + Ẋ · r y - Φ. · R x

Zeroing the speed then gives the relevant straight line equation for the speed zero line 19 according to

Because the speed zero line 19 always a straight line, in the most unfavorable case, a pentagon results for the relevant contact surface (hatched area 16b ), as 12 shows.

12 shows the resulting contact area with existing zero speed line 19 near a corner 20 , Since the centroid of the triangular surface to be subtracted (dotted surface part 16a ), the area centroid of the dotted triangular area can be determined 16a plus the hatched, actual contact area 16b calculate as sum of gravity. For the resulting quadrilateral total area (area parts 16a and 16b ) can now again according to the method described above, the missing contact edge 17 to calculate.

dabei wird der Boden über eine kreisförmige, starre Platte mit Radius r und konstanter Druckverteilung belastet. F beschreibt die aufgebrachte Kraft und s die Einsinkung. Die Querdehnzahl ν ist für kohäsionslose Böden näherungsweise konstant und wird z. B. bei der Auswertung des statischen Lastplattenversuches immer mit ν = 0,212 angesetzt.The definition of the one-dimensional modulus of elasticity in soil mechanics is:

The soil is loaded by a circular, rigid plate with radius r and a constant pressure distribution. F describes the applied force and s the sinking. The transverse strain number ν is approximately constant for cohesionless soils and is z. B. in the evaluation of the static load plate test always with ν = 0.212.

The gradient .DELTA.F / .DELTA.s has already been determined above, so that the following is to be done for the contact surface parameter .alpha. (With .nu. = 0.212):

at this definition sets the above-mentioned value γ to 2.1, which leads to suitable results. However, it has been found that the transverse strain number ν at different soil quality can vary. Accordingly, the factor γ can be in a range of 1.5 to 2.7 lie.

aus der Kontaktfläche A_C (Bezugszeichen 16) berechnen, deren Bestimmung oben bereits erläutert wurde.r _hyd represents the hydraulic comparison radius and can be according to

from the contact surface A _C (reference numeral 16 ), the determination of which has already been explained above.

To be able to compare the dynamic stiffness modulus E _{V, dynVerdichter} with deformation _moduli ; which have been determined by conventional, for example, standardized measuring methods, calibration measurements can be carried out or calibration tables can be evaluated.

The inventive method or a soil compacting device, such as a rammer or a vibrating plate, with the method according to the invention be operated it, the ground stiffness or the dynamic deformation module of the soil during the To determine compaction work. The method is particularly suitable good for Soil compacting devices in which the contact element relative performs long flight phases and in which due to significant rotational movement shares the Contact force and contact path often unpredictable, changing directions exhibit. Also well suited is the method of consideration different contact geometries or more effective, actual Contact surfaces. There is a significant difference to previously known measuring methods, which were used in particular for soil compaction rollers, in which, however, the contact surface and also the direction of the dominant contact force to the ground always is substantially constant or a priori is well predictable.

Soil compaction devices with a short or no flight phase can, using the method according to the invention however, also the soil stiffness and the dynamic soil deformation module determine.

13 shows a side view of a typical vibration tamper, in which the inventive method can be used.

Also Machines where of a substantially constant Contact behavior (vibration roller) is to go out, that can method described herein for determining the soil stiffness and the Use soil deformation module.

Claims (30)

Method for determining a soil property by means of a soil compaction device comprising a swinging contact element ( 1 ) for soil compaction, wherein - the contact element ( 1 ) is subjected to a contact force F _contact exerted by the ground and covers a contact path s _contact ; - The soil property is determined as a dynamic deformation _modulus E _{V, dynVerdichter} to

Α is a contact surface parameter for taking into account the actual contact surface ( 10 ) of the contact element ( 1 ) is with the ground; K _{dyn represents} the dynamic rigidity of the soil and is formed as a gradient of the contact force F _contact and the contact path s _contact . Method according to Claim 1, characterized in that the spatial components F _{C, i} (with i = x, y, z) to be calculated for the contact force F _contact of the contact _element ( 1 ) to the ground F C, X = m U (ẍ S - ẏ S · Ṅ + ż S · Φ.) - F ECC, X - F U, X + m U * G * sin (Φ) * cos (X) F C, Y = m U (ÿ S - ż S · Ẋ + ẋ S · Ṅ) - F ECC, Y - F U, Y + m U * G * cos (Φ) · sin (X) F C, Z = m U (z .. S - ẋẋ S · Φ. + ẏ S · Ẋ) - F ECC, Z - F U, Z + m U * G * cos (Φ) * cos (X) with - m _U is the mass of the contact element ( 1 ); - ẋ _S , ẏ _S , ż _S are the translation speeds in the center of gravity of the contact element ( 1 ); - ẍ S , ÿ S , z .. S are the corresponding accelerations; - Φ is the pitch angle around the y-axis; - X is the roll angle around the x-axis; - Φ, Ẋ and Ṅ are the corresponding rotational speeds in the pitch, roll and yaw directions (about the z-axis); F _{U, i} is a cutting force between the contact element ( 1 ) and the remaining soil compaction device; - F _{ECC, i} is the stimulating force of a contact element ( 1 ) stimulating vibration exciter ( 2 ); - g is the gravitational acceleration. Method according to claim 2, characterized in that the accelerations of the contact element ( 1 ) from the group ẍ S , ÿ S , z .. S by several on the contact element ( 1 ) provided accelerometers ( 7 ) are measured. A method according to claim 2, characterized in that the accelerations ẍ S , ÿ S , z .. S of the contact element ( 1 ) by at least one sensor ( 6a ) measured at one with the contact element ( 1 ) via a spring device ( 4 ) ( 5 ) is provided. Method according to one of claims 2 to 4, characterized in that - rotational accelerations Φ .., Ẍ and N .. by at least one on the contact element ( 1 ) sensor are measured; - The rotational speeds Φ., Ẋ and Ṅ are determined by simple integration of the rotational accelerations Φ .., Ẍ and N ..; and that - the pitch angle Φ and the roll angle X of the contact element ( 1 ) by two-fold integration of the rotational accelerations Φ .., Ẍ and N .. be determined. Method according to one of claims 2 to 5, characterized in that the exciting force F _ECC by a between the vibration exciter ( 2 ) and the contact element provided force measuring device is measured. Method according to one of claims 2 to 6, characterized in that - the vibration exciter ( 2 ) at least two counter-rotating, equal imbalance masses ( 3 ) whose phase angle is mutually adjustable and whose axes of rotation parallel to a Y-axis of the contact element ( 1 ) are directed; and that - the components of the exciting force F _ECC are calculated by the following relationship: F ECC, X (t) = EM · Ω 2 sin (φ phase / 2) · cos (Ω · t) F ECC, Y (t) = 0 F ECC, Z (t) = EM · Ω 2 cos (φ phase / 2) · cos (Ω · t) where EM is the resulting mass of rotating unbalanced masses ( 3 ), Ω is the exciting frequency of the vibration exciter ( 2 ) And φ _{phase represents} the phase angle between the two imbalance masses. Method according to one of claims 1 to 7, characterized in that - the soil compacting device is a vibrating plate or a vibrating tamper; and that - the contact force F _{contact is} determined to F contact = m U · Z .. S - F ECC, Z where m _{U is} the mass of the contact element ( 1 ) z .. S the acceleration of the contact element ( 1 ) In the direction of the contact normal and F _{ECC, Z is} the exciting force of the contact element ( 1 ) acting vibration exciter ( 2 ). A method according to claim 8, characterized in that the acceleration z .. S of the contact element ( 1 ) by one on the contact element ( 1 ) accelerometers ( 4 ) is measured. A method according to claim 8, characterized in that the acceleration z .. S of the contact element ( 1 ) is measured by a sensor located at one with the contact element ( 1 ) via a spring means () connected upper mass () is provided. Method according to one of claims 1 to 10, characterized in that - the vibration exciter ( 2 ) two counter-rotating, equal imbalance masses ( 3 ), whose phase position is predetermined and / or mutually adjustable; and that - the exciting force F _ECC is calculated by the following relationship: F ECC = EM · Ω 2 cos (φ phase / 2) · cos (Ω · t) where EM is the resulting mass of rotating unbalanced masses ( 3 ), Ω is the exciting frequency of the vibration exciter ( 2 ) and Φ _phase the phase angle between the two imbalance masses ( 3 ). Method according to one of claims 1 to 11, characterized in that the contact path s _contact is determined as follows: - determining the acceleration a _{P, z of} a force application point P ( 15 ) in the z direction a P, e.g. = z .. s + Ẍ · SP Y - φ .. · SP X - (φ. 2 + Ẋ 2 ) · SP Z Calculating the contact path s _contact by double integration of the acceleration a _{P, z} . Method according to one of claims 1 to 12, characterized in that for each time points in each case a pair of measuring points from the contact force F _contact and the associated contact path s _{contact is} formed. A method according to claim 13, characterized in that for those pairs of measuring points, during a loading phase, in which the contact element ( 1 ) increasingly presses against the ground, in each case a gradient dF _cotact / ds _{contact is} formed. A method according to claim 13 or 14, characterized in that the resulting gradient for the respective pairs of measurement points are averaged by a statistical method and that the resulting average value is determined as the dynamic stiffness k _dyn . Method according to one of claims 1 to 15, characterized in that - for the contact force F _contact and the contact path s _contact a dependent of the time t phase diagram is formed; and that - for a part of the phase diagram representing a loading phase in which the contact element ( 1 ) increasingly against the ground, a middle gradient dF _contact / ds _{contact is} formed, which represents the dynamic stiffness k _dyn . Method according to one of claims 1 to 16, characterized in that the contact surface Pa parameter α due to a resulting position of a force application point ( 15 ) of the contact force F _{contact is} determined. Method according to one of claims 1 to 17, characterized in that for determining the contact surface parameter α a centroid of the actual contact surface ( 12 ) of the contact element ( 1 ) is determined with the soil from a force application point ( 15 ) Of the contact force F _contact is determined. A method according to claim 18, characterized in that the force application point ( 15 ) independent of a centroid of a base of the contact element ( 1 ) and does not have to coincide with this. Method according to one of claims 1 to 19, characterized in that the contact surface parameter α is determined by:

where γ is a value in a range of 1, 5 to 2, 7, in particular the value 2.1 and r _{hyd represents} the hydraulic comparison radius and according to

from an actually effective contact surface A _{C of} the contact element ( 1 ) is calculated with the soil. A method according to claim 20, characterized in that for determining the effective contact area A _C, a part of the contact surface geometry, in particular a part of the outer boundary edges of the contact surface geometry is known and the missing part of the contact surface A _{C is} calculated from the knowledge of the centroid. Method according to one of claims 18 to 21, characterized in that - by sensors ( 7 ) the movement of the contact element ( 1 ) is detected when touching the ground; and that - on the basis of 7 ) information and the contact force F _contact the position and dimension of the inside of the base of the contact element ( 1 ) actual contact surface ( 10 ) and / or the force application point ( 15 ) is determined. Method according to one of claims 18 to 22, characterized in that for determining the force application point ( 15 ) of the contact force F _contact - caused by the contact force F _contact Nick spin acceleration of the contact element ( 1 ) with respect to a transverse to the direction of travel of the soil compaction device pitch axis ( 8th ), and - a rolling spin of the contact element ( 1 ) with respect to a roll axis extending in the direction of travel ( 9 ) by the sensors ( 7 ). Method according to one of claims 1 to 23, characterized in that a translational movement of the contact element ( 1 ) in the direction of the contact force F _contact by the sensors ( 4 . 5 ) is determined. A method according to claim 23 or 24, characterized in that due to the by the sensor ( 7 ) measured movements of the contact element ( 1 ) and an evaluation of the angular momentum set about the pitch axis ( 8th ) and around the roll axis ( 9 ) caused by the contact force F _{contact contact} torques about the pitch axis ( 8th ) and the roll axis ( 9 ). A method according to claim 25, characterized in that due to the contact torque and the already determined resulting contact force F _contact the lever arms with respect to the pitch axis ( 8th ) and the roll axis ( 9 ) and thus the position of the force application point ( 15 ) of the contact force F _contact . Method according to one of claims 1 to 26, characterized in that due to the position of the force application point ( 15 ) of the contact force F _contact the position of the centroid of the contact surface ( 12 ) be is true. Method according to one of claims 1 to 27, characterized in that due to the position of the centroid or the force application point ( 15 ) and a predetermined relationship of the contact surface parameters α is determined. Soil compaction device, comprising - a drive-driven vibration exciter ( 2 ); - one of the vibration exciter ( 2 ) acted upon contact element ( 1 ) for compacting the soil; and with a measuring system for determining a soil property, comprising at least one measuring sensor ( 6 . 7 ) for detecting a movement behavior of the contact element ( 1 ) having; characterized in that the measuring system is operated by a method according to one of claims 1 to 27. Ground compacting device according to claim 29, characterized characterized in that the soil compacting device is a vibrating plate or a rammer is.